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Climate extremes impact the function, structure, and composition of terrestrial ecosystems, while ecosystem responses to climate extremes differ with variations in frequency, intensity, and timing of the extreme event. We examined the canopy recovery processes following a typhoon disturbance in a cool-temperate deciduous forest in northern Japan based on 6-year data of canopy coverage imagery using a digital cover photography (DCP) approach that estimates canopy metrics relevant to leaf and woody masses, spatial dynamics, or arrangement of foliage elements. The DCP-derived imagery detected increases in leaf area index and foliage cover within 2~3 years after the typhoon (i.e., recovery to the pre-typhoon state). Meanwhile, the recovery in leaf area and foliage cover observed after 6 years resulted from a spatial re-arrangement of the foliage elements (i.e., small within-crown gap fraction, foliage clumping) with increasing canopy space availability. Thus, the recovery of the spatial arrangement of foliage elements after the typhoon to the pre-typhoon state takes longer than the recovery of the leaf and woody masses. This study provides an important ecological implication in terms of possible resilience adaptation for ecosystem function and structure following extreme climate events. Key words: digital camera imagery, climate extremes, ecosystem resilience, spatial canopy dynamics, foliage clumping. Les conditions climatiques extremes ont un impact sur la fonction, la structure et la composition des ecosystemes terrestres tandis que les reactions des ecosystemes aux conditions climatiques extremes different selon la frequence, l'intensite des evenements extremes et le moment ou ils surviennent. Nous avons etudie les processus de recuperation du couvert forestier a la suite d'une perturbation causee par un typhon dans une foret decidue sous un climat frais tempere dans le nord-est du Japon. L'etude repose sur 6 annees de donnees d'imagerie du couvert forestier obtenues en utilisant la methode de la photographie numerique du couvert (PNC). Cette methode estime les metriques du couvert forestier pertinentes a la masse de la matiere ligneuse et du feuillage, a la dynamique spatiale ou a l'organisation spatiale des elements du feuillage. Les images derivees de la PNC ont detecte une augmentation de l'indice de surface foliaire et du couvert de feuillage 2 ou 3 ans apres le passage du typhon (c.-a-d. recuperation correspondant a la situation qui prevalait avant le passage du typhon). Pendant ce temps, la recuperation de la surface foliaire et du couvert de feuillage observee apres 6 ans etait le resultat d'une reorganisation spatiale des elements du feuillage (c.-a-d. faible proportion de trous a l'interieur de la cime et presence de touffes de feuilles) avec l'augmentation de la disponibilite de l'espace dans le couvert forestier. Par consequent, apres le passage du typhon le retour de l'organisation spatiale des elements du feuillage a ce qu'elle etait avant le typhon prend plus de temps que la recuperation de la masse de la matiere ligneuse et du feuillage. Cette etude a d'importantes implications ecologiques en termes d'adaptation potentielle de la resilience dans le cas de la fonction et de la structure des ecosystemes a la suite d'evenements climatiques extremes. [Traduit par la Redaction] Mots-cles : images provenant d'un appareil photo numerique, conditions climatiques extremes, resilience des ecosystemes, dynamique spatiale du couvert forestier, presence de touffes de feuilles., Introduction Canopy is the aggregate of the leaves and woody materials of twigs and branches over an ecosystem scale. Plant leaves are the most essential canopy element constraining photosynthetic assimilation [...]

Abstract Background Changes in the timing of phenological events may cause the annual carbon budget of deciduous forests to change. Therefore, one should take such events into account when evaluating the effects of global warming on deciduous forests. In this article, we report on the results of numerical experiments done with a model that includes a phenological module simulating the timing of bud burst and other phenological events and estimating maximum leaf area index. Results This study suggests that the negative effects of warming on tree productivity (net primary production) outweigh the positive effects of a prolonged growing season. An increase in air temperature by 3°C (5°C) reduces cumulative net primary production by 21.3% (34.2%). Similarly, cumulative net ecosystem production (the difference between cumulative net primary production and heterotrophic respiration) decreases by 43.5% (64.5%) when temperatures are increased by 3°C (5°C). However, the positive effects of CO2 enrichment (2 × CO2) outweigh the negative effects of warming ( Conclusion Although the model was calibrated and validated for a specific forest ecosystem, the implications of the study may be extrapolated to deciduous forests in cool-temperate zones. These forests share common features, and it can be conjectured that carbon stocks would increase in such forests in the face of doubled CO2 and increased temperatures as long as the increase in temperature does not exceed 5°C.

This paper examines the morphological and physiological responses of an annual plant on the wide range of soil nutrient availability, including the photosynthetic activity of plants. Populations of Impatiens balsamina L. are raised over a wide range of densities (20-1,250 plants m-2) at four nutrient levels (1.7-37.7 g-Nm-2) in greenhouse, and three consecutive harvests are performed. The photosynthetic rate of an individual leaf and phenotypic properties of every organ of the plants are determined. The coefficient of intra-specific competitive intensity of the total yield-density equation is found to increase with growth and not vary significantly with nutrient availability. Increased supply of nutrients lead to an increase in Specific Leaf Area (SLA), Stem Weight Fraction (SWF) and light-saturated maximal photosynthetic rate (pmax), whereas Leaf Weight Fraction (LWF) decline with nutrient availability. Nutrient availability does not affect Leaf Area Ratio (LAR), Relative Growth Rate (RGR), Unit Leaf Rate (ULR), or the coefficient of variation of total individual weight. Under low nutrient conditions, plants allocate more dry matter to leaves than to stems, in order to maintain the quality of the leaves and the consequent activity of photosynthesis. Under high nutrient conditions, leaves have high SLA and can maintain high pmax because of high nitrogen concentration in them. Such leaves with high SLA construct a crowded canopy, leading to severe shoot competition. Under such conditions, plants allocate more dry matter to stems, resulting in less crowded canopy architecture with growth. Therefore, the intensity of competition under high nutrient conditions becomes similar to that under low nutrient conditions, with growth. [ABSTRACT FROM AUTHOR]